This invention relates to brushless alternators, and in particular to a brushless alternator for mounting to an engine as a component of an engine-generator set.
Brushless alternators for converting mechanical energy to electrical energy are well known. Such alternators usually have an exciter field assembly fixed to a housing and an exciter armature mounted on a rotary shaft and inductively coupled to the exciter field assembly. An electrical current is induced in the exciter armature, in accordance with well known electromagnetic principles, and the exciter armature is electrically connected, usually including a conversion to direct current, to a rotor which is also mounted on the shaft. A stator is fixed in the housing around the rotor and is inductively coupled to the rotor. Thereby, an output voltage is induced in the stator.
The stator, rotor, exciter field assembly, and exciter armature are all made of coils of wire wound around multiple thin steel laminations. The laminations are stamped from sheet stock, usually coated with a varnish for insulation and stacked together. Prior alternators have used different laminations for the stator and the exciter field assembly, which has required a relatively large investment in tooling for making the laminations, as well as a corresponding difficulty in making the housing and assembling the stator and the exciter field to the housing.
Prior brushless alternators have been either stand alone units or sometimes have been made as part of a self-contained internal combustion engine-generator set. When made as a component of an engine-generator set, the alternator housing has typically been mounted to the engine housing and the engine shaft coupled to the alternator shaft. This has involved a problem in design, since the engine, of which there are many types with different housing-shaft relationships, has defined the relationship between the alternator housing mounting and shaft mounting.
Cooling has also been a problem in prior alternators. Fans have usually been mounted on the alternator shaft to draw cooling air through the alternator. However, prior air flow paths were circuitous, taking many bends and encountering restrictions, such that cooling was not adequate, which degraded the efficiency of the alternator and promoted wear.